Traditionally, an elevator machinery consists of a hoisting motor which, via a gear, drives the traction sheaves around which the hoisting ropes of the elevator are passed. The hoisting motor, elevator gear and the traction sheaves are generally placed in a machine room above the elevator shaft. They can also be placed beside or under the elevator shaft.
Another known solution is to place the elevator machinery in the counterweight of the elevator. A system with a traditional elevator machinery placed in the counterweight is presented for example, in U.S. Pat. No. 3,101,130. A drawback with the placement of the elevator motor in this solution is that it requires a large cross-sectional area of the elvator shaft.
A third previously known technique is to use a linear motor as the hoisting motor of the elevator and to place it in the counterweight.
Using a linear motor as the hoisting motor of an elevator involves problems beacause either the primary part or the secondary part of the motor has to be as long as the shaft. Therefore, linear motors are expensive to use as elevator motors. A linear motor for an elevator, placed in the counterweight, is presented for example, in U.S. Pat. No. 5,062,501. However, a linear motor placed in the counterweight has certain advantages, such as the fact that no machine room is needed and that the motor requires but a relatively small cross-sectional area of the counterweight.
The motor of an elevator may also be of the external-rotor type, with the traction sheave connected directly to the rotor. Such a structure is presented for example, in U.S. Pat. No. 4,771,197. The motor is gearless. The problem with this structure is that, to achieve a sufficient torque, the length and diameter of the motor have to be increased. In the structure presented in U.S. Pat. No. 4,771,197, the length of the motor is further increased by the brake, which is placed alongside of the rope grooves. Moreover, the blocks supporting the motor shaft increase the motor length still further.
In U.S. Pat. No. 5,018,603, FIG. 8 presents an elevator motor in which the air gap is oriented in a direction perpendicular to the motor shaft. Such a motor is called a disc motor or a disc rotor motor. These motors are gearless, which means that the motor is required to have a slow running speed and a higher torque than a geared motor. In the motors of U.S. Pat. Nos. 5,018,603 and 4,771,197, the outermost part of the motor is the traction sheave, leaving the effective magnetic area of the motor windings inside the traction sheave. This is a disadvantage when the motor is required to have a high torque.